V23 / Bell 202 Modem
CMX624
DTMF Transmitter
Notes
Min.
-1.0
-
Typ.
0.0
+2.0
Max.
+1.0
-
Unit
dBm
dB
Level at TOP pin; tones in High Group
Twist (level of High Group tones WRT level of
Low Group tones)
4
Tone frequency accuracy (worst case)
-0.5
-
+0.5
%
Tx Filter and Output Buffer
Change in level at TOP pin caused by changing
bit 2 of FSK MODE Register
Notes
Min.
2.5
Typ.
3.0
Max.
3.5
Unit
dB
Buffer output signal swing;
5
2.2
-
-
Vp-p
Load greater than 500Ω.
Notes:
5. For each of the TXON (if enabled) and TXO pins, load between pin and V / 2.
DD
FSK Demodulator and Rx UART
Valid Input Level Range
Acceptable Twist (Mark level WRT Space level)
Acceptable Signal to Noise Ratio
Rx 1200bits/sec (V.23 mode)
Acceptable Rx Data Rate
Mark (Logical 1) Frequency
Space (Logical 0) Frequency
Rx 75bits/sec (V.23 mode)
Acceptable Rx Data Rate
Mark (Logical 1) Frequency
Space (Logical 0) Frequency
Rx 1200bits/sec (Bell 202 mode)
Acceptable Rx Data Rate
Mark (Logical 1) Frequency
Space (Logical 0) Frequency
Rx 150bits/sec (Bell 202 mode)
Acceptable Rx Data Rate
Mark (Logical 1) Frequency
Space (Logical 0) Frequency
Notes
Min.
-43.0
-7.0
Typ.
Max.
-9.0
+7.0
-
Unit
dBm
dB
6
-
-
-
7
8
20.0
dB
1188
1280
2068
1200
1300
2100
1212
1320
2132
Baud
Hz
Hz
8
8
8
TBD
TBD
TBD
75
390
450
TBD
TBD
TBD
Baud
Hz
Hz
1188
1180
2168
1200
1200
2200
1212
1220
2232
Baud
Hz
Hz
TBD
TBD
TBD
150
387
487
TBD
TBD
TBD
Baud
Hz
Hz
Notes:
6. Measured at point A in Figures 8a and 8b, for VDD = 5.0V. The internal threshold levels
are proportional to VDD. To cater for other supply voltages or different signal level ranges
the voltage gain of the Rx Input Amplifier should be adjusted by selecting the appropriate
external components as described in Section 1.6.1.
7. Flat noise in 300-3400 Hz band for V.23, 200-3400 Hz for Bell 202.
8. Set by Rx UART and Xtal frequency.
2100Hz Detector
Notes
Min.
2040
<2010
-
Typ.
Max.
2235
>2265
25
Unit
Hz
Hz
ms
ms
‘Will Decode’ Frequency Range
‘Will Not Decode’ Frequency Range
‘Off’ to ‘On’ time
-
-
-
-
9
9
‘On’ to ‘Off’ time
4.0
-
Notes:
9. 2100Hz detection requires a signal within the amplitude range given in the Rx Energy
Detector section.
2003 CML Microsystems Plc
21
D/624/7
CMLMICRO [ CML MICROCIRCUITS ]
